About 1 million people a year begin a mental slide called mild
cognitive impairment, or MCI, with forgetfulness that's somewhere
between healthy aging and Alzheimer's disease. Now this gray zone
is undergoing an evolution, with growing study of techniques to
help predict which MCI patients may be on a path to later dementia
- and who shouldn't worry.

Many doctors aren't waiting. A study published in the journal
Neurology last week found 70 percent of neurologists say they
prescribe Alzheimer's medications to at least some of their MCI
patients, hoping the drugs will slow their decline. That's a
startling number considering there's no proof yet the drugs can do
that even if doctors knew who's most at risk.

Still, it's becoming more and more clear that Alzheimer's starts
ravaging the brain at least a decade before memory problems appear.
Thus stalling it may require treating the earliest symptoms, just
as preventing a stroke begins with treating high blood pressure.

But to discover an early-stage therapy requires first
discovering whose MCI really is pre-Alzheimer's.

So when the National Institute on Aging and the nonprofit
Alzheimer's Association proposed new guidelines for diagnosing both
full-blown Alzheimer's dementia and that confusing MCI, they went
an extra step. The draft also offers a roadmap for researchers
testing new technology to help separate out the different types of
MCI.

On the list: experimental PET scans that check for abnormal
brain buildup of an Alzheimer's-linked gunk called beta-amyloid.
Bollesen, 78, is getting that and other brain scans at the Mayo
Clinic in a large study hunting for patterns that predict
progression.

The retired teacher gets embarrassed by his main MCI symptom -
forgetting the names of longtime colleagues - but says he doesn't
worry about getting worse.

"They haven't told me what I can expect in the future. ... I'll
think about it when they bring it up," says Bollesen, 78, of
Rochester, Minn. If he does worsen, he figures the researchers
"may have ideas of things I could be doing to delay it."

Here's the rub: Those technologies are becoming more available
for use outside of strict research studies. Already, doctors at
specialized medical centers can use MRIs to measure shrinkage of a
brain region called the hippocampus. They can give spinal taps to
look for that gooey amyloid in cerebrospinal fluid.

Soon, even the full-brain amyloid scans will be more available,
says Dr. David Bennett, director of Rush University Medical
Center's Alzheimer's program in Chicago.

Scientists haven't proven when a bad test result really means
brewing disease, or even if you can believe a bad test result.
Those spinal fluid measurements, for example, can vary as much as
30 percent from one sophisticated laboratory to another, says Dr.
Marilyn Albert of Johns Hopkins University.

"The last thing in the world you want to do is tell someone
they're destined to have Alzheimer's dementia when they're not,"
cautions Albert, who co-authored the draft guidelines and doesn't
want doctors jumping the gun.

And just harboring amyloid alone doesn't mean pending dementia,
as autopsy studies suggest a quarter of elderly people who die
without memory problems may harbor the buildup, adds Mayo's Dr. Ron
Petersen, who helped to first define MCI.

"Would I like to have amyloid in the brain? No, not
particularly but it doesn't necessarily mean I'm going to become
clinically demented in my lifetime," Petersen says.

For now, diagnosing MCI requires a good medical history and
standard memory tests. MCI is more than every so often losing your
car keys or struggling for a word, but not serious enough to
interfere with independent functioning. Worsening of episodic
memory - recalling new information - is seen more than other types
of memory loss in MCI that progresses to Alzheimer's, say the draft
guidelines, which will be finalized later this year.

Like so many with MCI, forgetting names sent Mac McNellis of
Chicago to the doctor nine years ago. He feared the dementia his
mother had suffered in her 90s, but he was relieved to learn he had
MCI. McNellis enrolled in a study at Rush that scans his brain
annually, and researchers advised mental and physical exercise.

Now 85, he plays golf and cards, and is a pro at Sudoku and
intricate woodworking. Then last fall, he experienced a new MCI
symptom - getting frustrated in unfamiliar places - and began an
Alzheimer's drug in hopes of slowing further decline.

"I just go with the flow," McNellis says.

But his wife, Gerry, says learning about MCI early was a big
help.

"Staying active was probably the most important thing," says
Gerry McNellis. "Fear of the unknown I think can really be
detrimental. If you have an idea that there are some things that
can be done within your own power, it's really helpful."